Fuente: WIPO "milk" 1433328 Preparing cheese-starter cultures MILK MARKETING BOARD 29 June 1973 [30 March 1972] 15118/72 Heading C6F A process for producing a concentrated (e.g. at least 5 X 1010 organisms per ml) culture of lactic acid bacteria comprises cultivating the microorganisms aseptically and anaerobically at pH 6-7 and passing the product to one chamber of a dialyzer having at least 3 cm2/ml membrane surface whereby the micro-organisms are retained but lactic acid and salts thereof pass through the membrane to a solution whose concentration of these materials is low but which has a high nutrient content so that nutrient passes back through the membrane to the micro-organisms, which are then recirculated for further fermentation until the required concentration is achieved. The process may be continuous, the solution receiving lactic acid being in a closed circuit. The product micro-organisms, may be frozen. The pH may be maintained at 6-7 by addition of NaOH or NH 4 OH. The ratio of micro-organismscontaining solution to dialyzing solution may be 1:10. The flow-rate in the micro-organism cycle is preferably such as to produce maximum turbulence at the membrane surface.